Expandable drinking flask



FIG. 1 is a front, top and right perspective of an expandable drinking flask showing my new design;

FIG. 2 is a rear, bottom and right perspective view thereof;

FIG. 3 is a front elevation view thereof;

FIG. 4 is a rear elevation view thereof;

FIG. 5 is a right side elevation view thereof;

FIG. 6 is a left side elevation view thereof;

FIG. 7 is a top plan view thereof; and,

FIG. 8 is a bottom plan view thereof.

The drinking flask is shown with a symbolic break in its height. The appearance of any portion of the article within the broken lines forms no part of the claimed design. The broken line showing of a lid is for the purpose of illustrating portions of the flask and forms no part of the claimed design. 

CLAIM The ornamental design for an expandable drinking flask, as shown and described. 